V-Band Clamp Nut Keeps Turbochargers Sealed

Turbochargers, which have long been used in heavy trucking, are increasingly being used in light trucks and autos to deliver the power of a V8 engine in a V6, resulting in lighter vehicles and better fuel economy. But V-Band Clamps, which seal off hot exhaust so the turbocharger can force compressed air into the intake, have presented a challenge when traditional fastening nuts loosen in the extreme heat and vibration turbocharger environment.

Preventing exhaust leaks
With exhaust temperatures reaching up to 1,300F, the V-Band Clamp assembly could quickly be compromised if exhaust leaks. With component temperatures reaching up to 1,000F around the turbocharger, nut-locking features using adhesive or nylon rings would burn up.

Vibrational fastener loosening, already a challenge in well-supported engine blocks, can be a greater challenge in turbochargers, which typically hang off the side of the engine, with less structural support, and consequently, more vibration.

Since V-Clamp nuts must run down the length of the long T-bolt stud, which can be six to eight times the body diameter of the nut, prevailing torque-type locking features can gall and wear out before the nut is properly seated. If this happens on the assembly line, each incident can cost up to $2,000 to stop the line, remove the engine, and remanufacture the V-Band Clamp assembly. For this reason, plain metal V-Clamp nuts are typically used -- but as soon as they lose tension they can start to back off, which can raise performance and warranty issues.

Spiralock's V-Band Clamp Nut has a unique internal thread form that is helping the trucking and auto industries withstand extreme turbocharger heat and vibration problems, while reducing cost, assembly, and warranty issues. This reengineered thread form adds a 30-degree wedge ramp at the root of the thread, which mates with standard 60-degree male thread fasteners.

The wedge ramp allows the bolt to spin freely relative to female threads until clamp load is applied. The crests of the standard male thread form are then drawn tightly against the wedge ramp, eliminating radial clearances and creating a continuous spiral line contact along the entire length of the thread engagement. This continuous line contact spreads the clamp force more evenly over all engaged threads, improving resistance to vibrational loosening, axial-torsional loading, joint fatigue, and temperature extremes.

When a major heavy truck turbo manufacturer was breaking T-bolts driving a clincher nut that galled on a V-Band Clamp assembly previously, they had to take the turbo off the production line to repair. Switching to the free-spinning Spiralock V-Band Clamp saved them the loss of about 15 V-Band Clamp assemblies per day at the plant, eliminating related production downtime and remanufacturing cost.

With higher heat in gasoline engines than in diesel engines, the US auto fleet may benefit the most from Spiralock's V-Band Clamp Nut. It's already being used on one of the first applications of dual turbo engines in light trucks.

Rob, that's just what I have been saying! It is interesting that in Formula 1 racing the turbocharged engines are limited to 1.5L as oppossed to the naturally aspirated engines at 3.0L. Just an aside, these engines put out over 700HP. We can get the horsepower we need to drive our vehicles with less fuel, but it will take lots of engineering to make them as reliable as the current engines. This is just one good example of an engineering "detail" that is critical to success.

I agree Naperlou. With all of the attention on the innovation going into EVs and hybrids, I think some of the innovation on traditional gas engines is getting overlooked. In the long run, improved internal combustion engines may save more gas than electric vehicles.

Way back (late 1960's) when I worked summers as a part-time janitor for a school district, they had cleaning supplies deliverd in fibre drums (sweeping compound, etc). The lids on these drums were retained with exactly the same form device with the band in a U or V form to lock the lid to the top rim of the drum and with either a draw screw or over-center-snap link to draw thins tight.

OK this is a high temp alloy as needed by the application, but this is not new.

I believe you missed the point they are trying to make. I would blame the author for not showing an illustration of the thread form. It is not the V-Band Clamp that they are talking about as new. It is the thread form that they refer to as Spiralock. By the way, this thread form is not new either. Someone just seem to be promoting it for a new found application.

Spiralok has been around for a long time, but engineering folks need to be reminded or newly presented with this product's capability, every so often. I still have a Spirolok demonstration assembly on my desk. It reminds me of this potential solution, every time I glance at it. Many coworkers have picked it up and examined it, over the years.

The part in the photo looked very familiar. I went to my "secondary" desk behind me and picked up the part. The photo looks identical except mine has a hole for safety wire. The inner part is made up of two 180 degree parts, each with a "thread" cut on the inside and the clamp holds both parts together. It is used on a Gulfstream G1 turboprop 40kw auxillary power unit. The plane itself was built in 1958! This mechanism was designed so one mechanic could hold the heavy generator in place while another attached the "nut" to remove the loading. The strap holds it all in place and is safety wired to prevent it from coming apart unexpectedly in the air, always bad juju! It was no doubt an expensive part. It appears that auto manufacturers have found a cheaper was to fabricate them, but it is most certainly not new.

A few weeks ago, Ford Motor Co. quietly announced that it was rolling out a new wrinkle to the powerful safety feature called stability control, adding even more lifesaving potential to a technology that has already been very successful.

It won't be too much longer and hardware design, as we used to know it, will be remembered alongside the slide rule and the Karnaugh map. You will need to move beyond those familiar bits and bytes into the new world of software centric design.

People who want to take advantage of solar energy in their homes no longer need to install a bolt-on solar-panel system atop their houses -- they can integrate solar-energy-harvesting shingles directing into an existing or new roof instead.

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